\section{Real-Time Hatching}
An important part of the game was for the player to be able to easily distinguish between lit and unlit parts of surfaces. If the game was to have a realistic look, it would have been hard to make unlit surfaces look natural. In reality, light usually blends, bleeds, refracts and reflects from surface to surface, which makes it difficult to have one surface be completely unlit and other surfaces in close proximity be brightly lit.

Focusing on trying to give the game a high-contrast black and white look, as opposed to a low-contrast grayscale, a rendering technique called \textit{hatching} \citep{renderBook} was chosen. It gives a hand-drawn effect (see Figure \ref{fig:Hatching}). The edges of objects are highlighted in black and the textures are shaded as if by hand. Instead of varying in light intensity through a grayscale gradient, the game is kept almost entirely black and white. The gradient was achieved through blending between textures (see Figure \ref{fig:HatchingPatterns}) with black strokes of varying density and spacing with relation to light intensity. This makes unlit parts easy to distinguish from slightly lit parts, as the unlit parts of surfaces are entirely black and the lit parts all have some degree of white in them. 

\begin{figure}[htbp]
\centering
\includegraphics[width=0.6\textwidth]{Pictures/Design/Hatching/3D_Hatching.png}
\caption{Examples of real-time hatching on 3D objects \citep{renderBook}.}
\label{fig:Hatching}
\end{figure}

\begin{figure}[htbp]
\centering
\includegraphics[width=0.6\textwidth]{Pictures/Design/Hatching/HatchingPatterns.png}
\caption{Hatching patterns to blend between. Note: this figure does not include the completely white and black textures, which are used to get completely white and completely black areas depending on intensity \citep{renderBook}.}
\label{fig:HatchingPatterns}
\end{figure}

